package hclwrite

import (
    "bytes"
    "io"

    "github.com/apparentlymart/go-textseg/v13/textseg"
    "Havoc/pkg/profile/yaotl"
    "Havoc/pkg/profile/yaotl/hclsyntax"
)

// Token is a single sequence of bytes annotated with a type. It is similar
// in purpose to hclsyntax.Token, but discards the source position information
// since that is not useful in code generation.
type Token struct {
    Type  hclsyntax.TokenType
    Bytes []byte

    // We record the number of spaces before each token so that we can
    // reproduce the exact layout of the original file when we're making
    // surgical changes in-place. When _new_ code is created it will always
    // be in the canonical style, but we preserve layout of existing code.
    SpacesBefore int
}

// asHCLSyntax returns the receiver expressed as an incomplete hclsyntax.Token.
// A complete token is not possible since we don't have source location
// information here, and so this method is unexported so we can be sure it will
// only be used for internal purposes where we know the range isn't important.
//
// This is primarily intended to allow us to re-use certain functionality from
// hclsyntax rather than re-implementing it against our own token type here.
func (t *Token) asHCLSyntax() hclsyntax.Token {
    return hclsyntax.Token{
        Type:  t.Type,
        Bytes: t.Bytes,
        Range: hcl.Range{
            Filename: "<invalid>",
        },
    }
}

// Tokens is a flat list of tokens.
type Tokens []*Token

func (ts Tokens) Bytes() []byte {
    buf := &bytes.Buffer{}
    ts.WriteTo(buf)
    return buf.Bytes()
}

func (ts Tokens) testValue() string {
    return string(ts.Bytes())
}

// Columns returns the number of columns (grapheme clusters) the token sequence
// occupies. The result is not meaningful if there are newline or single-line
// comment tokens in the sequence.
func (ts Tokens) Columns() int {
    ret := 0
    for _, token := range ts {
        ret += token.SpacesBefore // spaces are always worth one column each
        ct, _ := textseg.TokenCount(token.Bytes, textseg.ScanGraphemeClusters)
        ret += ct
    }
    return ret
}

// WriteTo takes an io.Writer and writes the bytes for each token to it,
// along with the spacing that separates each token. In other words, this
// allows serializing the tokens to a file or other such byte stream.
func (ts Tokens) WriteTo(wr io.Writer) (int64, error) {
    // We know we're going to be writing a lot of small chunks of repeated
    // space characters, so we'll prepare a buffer of these that we can
    // easily pass to wr.Write without any further allocation.
    spaces := make([]byte, 40)
    for i := range spaces {
        spaces[i] = ' '
    }

    var n int64
    var err error
    for _, token := range ts {
        if err != nil {
            return n, err
        }

        for spacesBefore := token.SpacesBefore; spacesBefore > 0; spacesBefore -= len(spaces) {
            thisChunk := spacesBefore
            if thisChunk > len(spaces) {
                thisChunk = len(spaces)
            }
            var thisN int
            thisN, err = wr.Write(spaces[:thisChunk])
            n += int64(thisN)
            if err != nil {
                return n, err
            }
        }

        var thisN int
        thisN, err = wr.Write(token.Bytes)
        n += int64(thisN)
    }

    return n, err
}

func (ts Tokens) walkChildNodes(w internalWalkFunc) {
    // Unstructured tokens have no child nodes
}

func (ts Tokens) BuildTokens(to Tokens) Tokens {
    return append(to, ts...)
}

func newIdentToken(name string) *Token {
    return &Token{
        Type:  hclsyntax.TokenIdent,
        Bytes: []byte(name),
    }
}
